Background: In the developing world, such as the sub-Saharan African region, HIV/AIDS has worsened the impact of under-nutrition in children. HIV infected children are highly vulnerable to under-nutrition. Therefore, the objective of this systematic review and meta-analysis was to estimate the pooled prevalence of under-nutrition, and the pooled effect sizes of associated factors among HIV-infected children in sub-Saharan Africa.Methods: The primary studies for this review were retrieved from PubMed/ MEDLINE online, Science Direct, Hinari, web of science, CINHAL, EMBASE, WHO databases, Google, and Google Scholar databases. The articles selected for this meta-analysis were published between 2010 and 2020. The last search date was 18 October 2021. The data was extracted in Microsoft Excel format and exported to STATA Version 14.0. A random effect meta-analysis model was used. Heterogeneity was evaluated by the I2 test. The Egger weighted regression test was used to assess publication bias.Results: We retrieved 847 records from these databases. Of which records, 813 were excluded due to different reasons and 34 studies were included in the final analysis. The pooled prevalence of stunting, underweight and wasting in HIV infected children was 46.7% (95% CI; 40.36-53.07, I2 = 98.7%, p < 0.01), 35.9% (95% CI; 30.79-41.02, I2 = 97.4% p < 0.01), and 23.0% (95% CI; 18.67-27.42, I2 = 96.9%, p < 0.01) respectively. The advanced WHO HIV/AIDS clinical staging (III&IV) [OR = 6.74 (95%: 1.747, 26.021), I2 = 94.7%] and household food insecurity were associated with stunting [OR = 5.92 (95% CI 3.9, 8.87), I2 = 55.7%]. Low family economic status [OR = 4.737 (95% CI: 2.605, 8.614), I2 = 31.2%] and increased feeding frequency [OR = 0.323 (95% CI: 0.172, 0.605), I2 = 69.8%] were significantly associated with under-weight. Anemia [OR = 2.860 (95% CI: 1.636, 5.000), I2 = 74.8%] and diarrhea in the previous month [OR = 4.117 (95% CI: 2.876, 5.894), I2 = 0.0%] were also associated with wasting among HIV infected children in sub-Saharan Africa.Conclusions: The pooled prevalence of under-nutrition among HIV infected children was high. Nutritional assessment and interventions need great attention as a part of HIV care for HIV positive children. The implementation of policies and strategies established by national and international stakeholders in ART care centres should take a maximum emphasis on reducing under-nutrition among HIV infected children. [ABSTRACT FROM AUTHOR]